When a patient's own heart valves (the mitral valve, the tricuspid valve, the aortic valve, or the pulmonary valve) mutate due to congenital or acquired diseases and hence the valves are unable to open and close normally, health and even life may be adversely affected. The mutations of the heart valves include opening incompletely and closing incompletely, both the two situations may result in increase of cardiac load, and whether the heart can normally work under the increasing load is a main basis that determines whether the human body heart valves need to be replaced.
Implantation of artificial heart valves by interventional operations causes small traumas to human bodies and has a low invasion degree, and thus it is applied more and more widely. This operation can form a small incision with a diameter of several millimeters on the skin of a patient on the premise of no use of scalpel, through the incision the vasculature system of a human body can be accessed and a transport channel can be established, and an artificial heart valve (i.e., a stent) can be transported by a special transport system to the heart and replace a defective human body valve.
An artificial heart valve replacement device in the prior art generally includes a mesh stent made of memory metal material and a clover-shaped valve that is sewed in the stent and can be opened unidirectionally, referring to FIG. 1, the stent includes three parts, which are an aortic stent 1, a valve stent 2, and a right ventricular inflow tract stent 3, and at least one T-shaped fixed ear 10 is arranged at a top edge of the stent.
In an operation, an artificial valve replacement device is transported to an implantation point by a transport system. The transport system fixes the artificial valve replacement device on a stent fixing head, a front end of the stent fixing head is provided with a streamline guiding head, a core tube extends through the stent fixing head and is connected with the guiding head, and the core tube, the stent fixing head, and the guiding head cooperatively form a sheath core. When implanting the artificial valve, the artificial valve replacement device is positioned to engage with the stent fixing head of the transport system, a sheath tube is sheathed on the outside of the sheath core, and the stent is kept in a compressed status; the sheath tube and the sheath core carrying the artificial valve replacement device is transported from an inlet of a blood vessel to a location of a diseased valve, and the artificial valve replacement device is then released; the stent will expand under the action of the body temperature and push leaves of the artificial valve towards the wall of the blood vessel to complete the positioning, afterwards, the sheath tube and the sheath core are drawn out
Before the artificial valve replacement device is released, it must be mounted in the transport system stably. If the artificial valve replacement device is accidentally released, the life safety of the patient will be seriously threatened.
In the transport system, the artificial valve replacement device is fixedly mounted on the stent fixing head. FIG. 2 shows a structure of a conventional stent fixing head, wherein an outer wall of the stent fixing head defines a positioning groove 11. When mounting the artificial valve replacement device, the fixed ear 10 of the stent of the artificial valve replacement device is fittingly embedded in the positioning groove 11. In the prior art, a thickness of the fixed ear of the stent is generally about 0.4 mm, correspondingly, a depth of the positioning groove is also about 0.4 mm, that is, the depth is very small. Since there is a clearance with a width of about 0.1-0.2 mm between the stent fixing head and the inner wall of the sheath tube, and the transport system needs to pass the tortuous and complex vasculature system to transport the artificial valve replacement device to the implantation point, when the transport system turns, the sheath tube is bent and deformed, and thus the stent fixed ear is prone to slide out along the clearance, resulting in disengagement of the artificial valve replacement device.
Furthermore, in order to guide the fixed ear of the stent to enter the positioning groove successfully and facilitate the release of the artificial valve replacement device in the operating process, as shown in FIG. 3, an opening part of the positioning groove is provided with a chamfer 12, and a peripheral edge of the positioning groove is also provided with a chamfer 13, however, the chamfers are easier to cause disengagement of the artificial valve replacement device.
When not being used, the stent of the artificial valve replacement device is in a folded state, and is a compact tubular structure fabricated by machining memory metal or shape memory alloy using laser cutting. After the stent expands in a human body, it will be in tight contact with a blood vessel wall. If a thickness of the stent increases, not only does the processing difficulty increase, but also the compliance and expanding performance of the stent are affected.